Re: [PATCH bpf-next v3 2/2] bpf: Add show_fdinfo for kprobe_multi

[Tao Chen]

在 2025/6/19 09:46, Alexei Starovoitov 写道:
> On Mon, Jun 16, 2025 at 6:03 AM Tao Chen <chen.dylane@xxxxxxxxx> wrote:
> > Show kprobe_multi link info with fdinfo, the info as follows:
> >
> > link_type:      kprobe_multi
> > link_id:        1
> > prog_tag:       a15b7646cb7f3322
> > prog_id:        21
> > type:   kprobe_multi
> > kprobe_cnt:     8
> > missed: 0
> > cookie           func
> > 1                bpf_fentry_test1
> > 7                bpf_fentry_test2
> > 2                bpf_fentry_test3
> > 3                bpf_fentry_test4
> > 4                bpf_fentry_test5
> > 5                bpf_fentry_test6
> > 6                bpf_fentry_test7
> > 8                bpf_fentry_test8
> >
> > Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx>
> > ---
> >   kernel/trace/bpf_trace.c | 32 ++++++++++++++++++++++++++++++++
> >   1 file changed, 32 insertions(+)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 2d422f897ac..fcf19e233b5 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2623,10 +2623,42 @@ static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
> >          return err;
> >   }
> >
> > +#ifdef CONFIG_PROC_FS
> > +static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link *link,
> > +                                        struct seq_file *seq)
> > +{
> > +       struct bpf_kprobe_multi_link *kmulti_link;
> > +       char sym[KSYM_NAME_LEN];
> > +
> > +       kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
> > +
> > +       seq_printf(seq,
> > +                  "type:\t%s\n"
> > +                  "kprobe_cnt:\t%u\n"
> > +                  "missed:\t%lu\n",
> > +                  kmulti_link->flags == BPF_F_KPROBE_MULTI_RETURN ? "kretprobe_multi" :
> > +                                        "kprobe_multi",
> > +                  kmulti_link->cnt,
> > +                  kmulti_link->fp.nmissed);
> > +
> > +       seq_printf(seq, "%-16s %-16s\n", "cookie", "func");
> > +       for (int i = 0; i < kmulti_link->cnt; i++) {
> > +               sprint_symbol_no_offset(sym, kmulti_link->addrs[i]);
> > +               seq_printf(seq,
> > +                          "%-16llu %-16s\n",
> > +                          kmulti_link->cookies[i],
> > +                          sym);
>
> Why call sprint_symbol_no_offset() directly ?
> %pB is fine.
> +off doesn't disclose anything.
>
> pw-bot: cr

My problem, sorry for that, i had some issues with using printk to show 
func name directly before. Actually, i used it incorrectly. How about 
%pS, it looks more accurate. Thanks!

%pB format
cookie           func
8                __pfx_bpf_fentry_test1+0x10/0x10
2                __pfx_bpf_fentry_test2+0x10/0x10
7                __pfx_bpf_fentry_test3+0x10/0x10

%pS format
cookie           func
8                bpf_fentry_test1+0x0/0x20
2                bpf_fentry_test2+0x0/0x20
7                bpf_fentry_test3+0x0/0x20

--
Best Regards
Tao Chen